Feed water heaters for steam turbine plant



July 6, 1965 H. H. L. RITZ ETAL FEED WATER HEATERS FOR STEAM TURBINE PLANT 7 Sheets-Sheet 1 Filed April 10, 1961 July 6, 1965 H. H. L. RITZ ETAL FEED WATER HEATERS FOR STEAM TURBINE PLANT Filed April 10. 1961 '7 Sheets-Sheet 2 FEED WATER HEATERS FOR STEAM TURBINE PLANT Filed April 10. 1961 7 Sheets-Sheet 3 O O I, .5 O k x0 O O Q I I i5 6 H U I0 2 [3 11'- a \J o Q x Q O O O O O O O O O O I b 'i 7 H. H. L. RITZ ETAL Ill l llll'l FEED WATER HEATERS FOR STEAM TURBINE PLANT July 6, i965 Filed A ri; 10. 1961 m mq 7 y 1965 H. H. L. RITZ ETAL 3,193,002

FEED WATER HEATERS FOR STEAM TURBINE PLANT Filed April 10, 1961 '7 Sheets-Sheet 5 July 6, 1965 H. H. L. RlTZ ETAL 7 Sheets-Sheet 6 y 1965 H. H. L. RITZ ETAL v3,193,002

FEED WATER HEATERS FOR STEAM TURBINE PLANT Filed April 10. 1961 7 Sheets-Sheet '7 United States Patent 3,193,002 FEED WATER HEATERS FOR STEAM TURBINE PLANT Hugo Heinrich Ludolf Ritz and Vincent Power, Newcastle-upon-Tyne, England, assignors to C. A. Parsons & "Company Limited, Newcastle-upon-Tyne, England Filed Apr. 10, 1961, Ser. No. 101,905 Claims priority, application Great Britain, Mar. 10, 1961, ,923/61 4 Claims. (Cl. 165-139) This invention relates to feed water heaters for steam turbine plant.

It is common practice in steam turbine plants to construct feed heaters in the form of one or more banks of U-shaped tubes located in a casing the tubes having their ends secured in a common flat tube plate. The feed water is circulated through the tubes and steam is circulated over the outside of the tube bank to raise the temperature of the feed water prior to its recirculation by means of a boiler feed pump to a steam boiler.

In some instances it is desirable to have the boiler feed pump on the inlet side of the feed heater or heaters in which case the pressure of the feed water entering the feed heaters is higher than in the more normal case when the pump is placed between the feed heaters and the boiler. The higher pressures involved require tube plates of increased thickness and this leads to practical difiiculties in the spacing of the tubes and the joining of the tubes to the tube plate.

A further disadvantage with the type of feed heater using U-shaped tubes is that the condensed steam drains from the lower end of the vessel containing the tube nest which is normally the end remote from the inlet for feed water to the tubes. From a heat transfer viewpoint it is desirable that the condensate should be giving up heat to the incoming feed water and this is not possible unless the condensate is raised up the casing to flow over the inlet ends of the tubes.

The object of the present invention is to provide an improved construction of feed heater which substantially overcomes the above disadvantages.

The invention in brief consists in a feed water heater for steam turbine plant comprising a casing, an internal duct located within the casing to form an annular space between the outer surface of the duct and the inner surface of the casing, a header at each end of the duct each header comprising curved walls, a plurality of tubes arranged in said annular space, inlet ends of the tubes passing through the curved walls of one header and outlet ends passing through the curved walls of the other header, inlet and outlet pipes for feed water attached to one of the headers, one pipe passing through said header and communieating with the internal duct, to provide a flow path for feed water through the headers, tubes and internal duct inlet means for steam adjacent the header connected to the outlet ends of the tubes and outlet means for condensed steam adjacent the other header; the flow path for steam through the casing being divided into three sections, at desuperheater section, a condensing section and a condensate section, the condensing section being formed by dividing the annular space into a number of sector shaped compartments, steam from the desuperheating section entering at least one of the compartments flowing in an axial direction towards the condensate section then flowing in the reverse direction in an adjacent compartment until finally it enters the condensate section.

The invention includes a feed heater substantially as described below with reference to the accompanying drawings in which:

FIGURE 1 is a longitudinal section through a feed water heater in accordance with one form of the invention;

FIGURE 1a is a reproduction of part of FIGURE 1 showing only one tube for explanation purposes;

FIGURE 2 is an enlarged section on line 11-11 of FIGURE 1;

FIGURE 3 is an enlarged section on line IIIIII of FIGURE 1;

FIGURE 4 is an enlarged section on line IV-lV of FIGURE 1;

FIGURES 5a and 5b are respectively top and bottom halves of a longitudinal section through a feed water heater in accordance with an alternative form of the invention;

FIGURE 6 is a section on line VI-VI of FIGURE 5a;

FIGURE 7 is a section on line VIIVII of FIG- URE 5a;

FIGURE 8 is a view in perspective with parts broken away and sectioned and showing by means of arrows through the desuperheated section of the heater of FIG. 1; and

FIGURE 9 is a view in perspective with parts broken away and sectioned and showing by means of arrows the steam flow path through the condensing section of the heater of FIG. 1.

In carrying the invention into effect in the forms illustrated by way of example and referring to FIGURE 1 a feed water heater for steam turbine plant comprises a casing I, an internal duct 2 located within the casing such that an annular space 3 is formed between the outer surface of duct 2 and the inner surface of casing 1. At each end of the duct 2 is a header; a header 4 is in communication with the duct 2 whilst header 5 is sealed ofi" from duct 2 by an inlet duct 6 passing through header 5 and communicating with duct 2.

In space 3 is arranged a plurality of tubes 7 indicated by their centre lines in FIGURE 1. The inlet ends of the tubes are in communication with header 4 and the outlet ends communicate with header 5 surrounding inlet duct 6. Each tube as can best be seen in FIGURE 1:: comprises three main sections, a first section a in which the tube follows a sinuous path in a substantially single plane, a second section b in which the tube forms a coil lying in a substantially single plane the tube forming successive turns of the coil one within the other and then being reversed to form successive turns of the coil one outside the other, and a third and substantially straight section 0 lying in substantially the same plane as the coil which third section communicates with header 5.

The annular space 3 is divided into two concentric annular spaces 3a, 3b by a cylinder 8 one end of which 8a is closed and surrounds duct 2 whilst the other end adjacent tube sections a is open. The cylinder 8 separates the second'and third sections of the tubes, the coiled second sections lying enclosed by cylinder 8 in space 3a and the straight third sections in space 3b.

The space 312 is subdivided into a number of sector shaped compartments by radially extending walls or baflies 9a-9h as can best be seen from FIGURE 2. In the space 3b are circumferentially disposed baffles 10; bafiles are placed at intervals along the axis of the heat exchanger as can be seen in FIGURE 1. They do not extend for the full circumferential extent of the heat exchanger. The edges of the uppermost 'bafile 10 can be seen in FIGURE 2, being represented by the full lines ex- These tending radially across space 31 The edges of the lower baffle 10 are shown dotted in space 3b.

In the part of the heater containing the first sectionsof the tubes the annular space 3- is, likewise divided into sections by radially extending walls or bafiles 11 as can be seen in FIGURE 3. The walls 11 extend from the walls of an open ended cylinder 11a which encloses the tubes in this section; The bafiles 11 also support further bafiles 12 (FIGUREl) in a planeat right angles thereto and erally longitudinal direction over the tubes in the third section and is deflected at intervals bybaflieslO. ;In this part of the feedheater, in which the steam is in contact with the third sections of the tubes in space 312, the steam has its superheat removed by the feed water in the tubes.

When the desuperheated steam reaches the lower end of said third sections of the tubes it passes through an opening 8b in the cylindrical wall 8 which opening extends on either side of battle 9a. It then flows upwards in the two sectors A A (see FIGURE 2) on eitherside of battle 9a, over the second sections of the tubes. n reaching the upper region of the said second sections its passes over the top of radial bafiles 9c,9[d and flows through sectors B B ina. downward direction. "It then passes beneath baffies 92,9 and then flows upwards in sectors C C On reaching theupperregion ofsectors C and C its passes over the top of battles 9g, 9h and flows downwardly in sectorsD and D During its flow upwards and downwards in: the various sectors the steam is C011. densing and the condensate collects in the lower portion of the feed heater surrounding the first sections of the tubes. f

The condensate level is controlled at, a level below the aforementioned inlets for steam from the desuperheater section that is to say below the second section of the tubes. Theconden'sat'e leaves the feed heater via drain 14 and in its passage to-the drain it follows a path which is governed by the baffles 12 which direct it in a direction substantially parallel to the tube axes for most of its. passage;

The steam thereforepasses through three separate stages, a desuperheater stage in space 3b whenit i's'in contact with the third sections. of the tubes, a condensing stage in space 3a whenit is in contact with the second sections of thetubes and a water or condensate stage where it isin contact with. the first sections of the tubes and from which stage it is conducted from the'feed heater.

flows over the third In the form shown in the drawing the header 5 is formed integrally with an end cover for the feed heater casing but this is not essential to the functioning of the heater. v Y

' In some instances where the length'of height of the heater is' not important the desuperheater, condensing and condensate sections can be arranged successively one after the other in the direction of the axis of the casing and in the direction of steam flow; This, form is shown in FIGURES5-7.

. In this arrangement the condensate, and condensing section remain substantially the same;v For convenience of assembly the shape of the tubes in the desuperheater section is made the same as those in the. condensate section so that the tubes, are reversible.

With the arrangements of FIGURES 5-7 a smaller diameter of heater is I achieved-and therefore the casing thickness 'is'reduced. Alfurtheradvantage of this type is that the superheatersteamis in the upper part of the casing only and does not extend over a considerable portion of its length as in the case of the other arrangementshown in FIGURES 1-4. This leads to reduced expansion of the casing. a

In both arrangements, however, the tube bankisfixed only at one end the other end; of the tube bank and associated header can expand relative totthecasing.

. In the forms illustratedthe feed water'inlet and outlet pipes are .in the header 7 adjacent the V steam inlet but this is, not essential. For example the feed water inlet and outlet pipes could be in the header ,4 in which case the inlet pipe 6 for the feed water would be the pipe conveying water into the header 4 and into the inlet ends of the tubes and the outlet pipe 611 would communicate with the internal duct 2 and seal of the header 4, from this duct.

' The condensing section b of the feed heater shown in FIGURES. 5-7 is divided by radial walls 9 in similar fashion to the heatershown in FIGURES 14..

We claim 1. A feed water heater for steam turbine plant comprising afcasing, an internal duct located within the casing and extending through the major portion of the length of saidcasing to forman annular space between the outer surface of the duct and the inner surface of the casing, a

header at each end of the duct each header comprising curved walls, a plurality of tubes arranged in radial planes within said annular space, inlet ends of all the tubes passing through the curved walls of one header and outlet ends of all thetubespassing through the curved walls of the other header, inlet and outlet'pipes for feed water attached to one of theheaders, one pipepassing through said headerrand' communicating with the internal duct, to provide a flow pathrfor feed water through the headers, tubes and through the full. length of the internal duct, inlet means for steamfladjacent'the header connected to the outlet ends of the tubes, and'outlet means for condensed steam adjacent theother; header; the flow path for steam through the casing comprising a desuperheater FIGURE 4 shows, the arrangement of the tubes where they enter header 5. r

The construction described allows. substantially full utilisation of the available space by virtue ofthe tube arrangement particularly in the second or condensing section, and the condensate is in. heat transfer relationship with the feed water entering 'the tubes without. the. need for forced.- circulation of-the condensate. a

Further by virtue of the fact that theheaderscomprise curved surfaces and the, ends oi the tubes pass through these, curved surfacesa flat tube plate is dis;

pensed=with and consequently reduced wall thicknesses are permissible with consequent lessening of leakageproblems.

section, a condensing section-and a condensate section, the condensing section being located immediately above the condensate section and having radial walls; therein dividing the annularspace into a number of sector-shaped compartments extending from the surface of condensate in the condensate section there being a passage at one axial end of each radial wall, the passage at the end of' I the annular space is divided into two separate annular spaces, an inner space and outer space, by, a cylindrical wall the tubes in the inner space forming the condensing section and the tubes in the outer space the desuperheating section, the inner space being sealed off from the outer space at the end of the cylinder adjacent the steam inlet by a wall joining the said cylindrical wall and the header receiving the outlet ends of the pipes.

3. A feed water heater as claimed in claim 1 in which the desuperheating, condensing and condensate sections are arranged successively one after the other in the direction of the casing axis and in the main direction of steam flow.

4. A feed water heater as claimed in claim 3 in which the tubes in the condensate section are of sinous form and the tube bends are interleaved by baifies extending in a circumferential direction from radial walls.

6 References Cited by the Examiner UNITED STATES PATENTS FOREIGN PATENTS 11/54 France.

9/55 Germany.

CHARLES SUKALO, Primary Examiner.

15 FREDERICK L. MATTESON, JR., Examiner. 

1. A FEED WATER HEATER FOR STEAM TURBINE PLANT COMPRISING A CASING, AN INTERNAL DUCT LOCATED WITHIN THE CASING AND EXTENDING THROUGH THE MAJOR PORTION OF THE LENGTH OF SAID CASING TO FORM AN ANNULAR SPACE BETWEEN THE OUTER SURFACE OF THE DUCT AND THE INNER SURFACE OF THE CASING, A HEADER AT EACH END OF THE DUCT EACH HEADER COMPRISING CURVED WALLS, A PLURALITY OF TUBES ARRANGED IN RADIAL PLANES WITHIN SAID ANNULAR SPACE, INLET ENDS OF ALL THE TUBES PASSING THROUGH THE CURVED WALLS OF ONE HEADER AND OUTLET ENDS OF ALL THE TUBES PASSING THROUGH THE CURVED WALLS OF THE OTHER HEADER, INLET AND OUTLET PIPES FOR FEED WATER ATTACHED TO ONE OF THE HEADERS, ONE PIPE PASSING THROUGH SAID HEADER AND COMMUNICATING WITH T THE INTERNAL DUCT, TO PROVIDE A FLOW PATH FOR FEED WATER THROUGH THE HEADERS, TUBES AND THROUGH THE FULL LENGTH OF THE INTERNAL DUCT, INLET MEANS FOR STEAM ADJACENT THE HEADER CONNECTED TO THE OUTLET ENDS OF THE TUBES AND OUTLET MEANS FOR CONDENSED STEAM ADJACENT THE OTHER HEADER; THE FLOW PATH FOR STEAM THROUGH THE CASING COMPRISING A DESUPERHEATER SECTION, A CONDENSING SECTION AND A CONDENSATE SECTION, THE CONDENSING SECTION BEING LOCATED IMMEDIATELY ABOVE THE CONDENSATE SECTION AND HAVING RADIAL WALLS THEREIN DIVIDING THE ANNULAR SPACE INTO A NUMBER OF SECTOR-SHAPED COMPARTMENTS EXTENDING FROM THE SURFACE OF CONDENSATE IN THE CONDENSATE SECTION, THERE BEING A PASSAGE AT ONE AXIAL END OF EACH RADIAL WALL, THE PASSAGE AT THE END OF 